That number, according to Levin, should be enough to provide counterterrorism and air support for Afghan forces, while continuing the U.S. military training mission in the country.
“We have no indication whatsoever of a withdrawal completely from Afghanistan,” according to Lt. Gen. Mark Milley, the No. 2 commander of all U.S. and coalition forces in country, said earlier this month.
American troops are already in the midst of shuttering bases and curtailing combat operations in the country, allowing Afghan National Security Forces to take the lead.
U.S. and NATO leaders are still negotiating with Kabul on exactly how many American and allied troops will remain in Afghanistan after the 2014 deadline.
However, Levin noted the eventual troop numbers for postwar Afghanistan will be irrelevant, if Washington and Kabul cannot agree on what the mission for those forces will be.
"It’s more important what their function is" rather than how many American boots on the ground there will be in the country after 2014, according to the Michigan Democrat.
That said, securing a bilateral security agreement is vital before any planning for a U.S. postwar force can begin, he added.
The security pact, once agreed to by Kabul, will lay the groundwork for a postwar American force and grant legal immunity for U.S. troops in that force.
"We have to have [an] ... agreement or else there won’t be any troops, and it’d be Iraq all over again which would be a mistake," Levin said.
Lack of an immunity deal for U.S. troops was a crucial factor in the failed attempt to set up a postwar security deal in Iraq and set the stage for the recent wave of sectarian violence against Iraqi forces and civilians in the country.
But fraying relations between Washington and the Karzai government have cast serious doubt over whether a postwar deal could be reached.
The Obama administration revived the “zero option” plan to leave no U.S. troops in the country after 2014 after a contentious meeting with Karzai in July.
However, top U.S. military leaders claimed that would be disastrous, further complicating the planned American withdrawal scheduled for next April.
— Jeremy Herb contributed to this report.